SINGLE-COIL TO AGGREGATE TRANSITION OF SULFONATED POLYSTYRENE IONOMERS IN XYLENE STUDIED BY DYNAMIC LIGHT-SCATTERING

A single-coil to aggregate transition in the zinc salts of sulfonated polystyrene ionomers in xylene was studied by dynamic light scattering . As the polymer concentration was increased in the dilute regime, the measured average diffusion coefficient of the polymer molecules decre ased, and it was accompanied by a broadening in the distribution of th e coefficient. Spectral analysis of the light scattering autocorrelati on function revealed a clear transition from a single- to a dual-decay rate mode with increasing solute concentration, the faster being iden tified as the diffusion of isolated coils. Thus the slowing-down of th e average diffusion with increasing polymer concentration was ascribed to the emergence of aggregates. The overall weight fraction of the ag gregates, however, remained low.